Patent GB-639583-A (GB)
Title: Improvements in and relating to filament forming apparatus
IPC: H01K3/04
Filed: 1947-07-25
Abstract: 639,583. Making electric lamp filaments. BRITISH THOMSON-HOUSTON CO., Ltd. (General Electric Co.). July 25, 1947, No. 20114. [Class 39 (ii)] Apparatus for shaping a long helically coiled filament 33 into one of planar type comprises an anvil member 44 and a pair of fingers 28 mounted in opposed relation thereto, the anvil and fingers being relatively movable and arranged to receive and grip a turn of the wire coil between them in the manner shown in Fig. 8, the fingers being also arranged to have a further movement whereby they are swung around the opposite sides of the anvil to bend the wire coil around it as shown in Fig. 10. The device comprises a horizontal bracket 3 projecting laterally from a vertical column 1, Fig. 1 (not shown), and provided with a horizontal guide block 21 and retaining members for a front slide 38 carrying the horizontally extending anvil 44 in the form of a thin blade with a wedge shaped nose 45 which is preferably inclined at an angle to the vertical, corresponding approximately to the pitch of the wire coil. A circular flanged head 24 located a short distance above the face of the guide block 21 provides a rest for the coil to be shaped, and a hollow stem extending downwardly from the head is connected by a tube to a heater, e.g. an electric heating coil, for supplying heated air or other gas to the part of the filament in the region of the anvil. The stem supporting the flanged head 24 provides, in the part thereof between the head and the guide block 21, a pivot for a pair of members 25, 26 carrying the coilforming fingers 28, preferably consisting of rods or blades of hardened steel, which are clamped in recesses in the holders 25, 26 by plates 29. In the rear or inoperative position of the fingers 28 the adjacent edges 27 of the holders 25, 26 are in abutment, as shown. The rear slide 39 is guided in ways 73 formed in an upper base plate, and is held down by a retaining strap 74. At its front, or inner end the slide 39 is forked to form a pair of forwardly extending spaced arms 76 which receive between them the front end or tongue of the guide block 21 when the rear slide is advanced towards the anvil, and the arms 76 are provided with transverse slots or grooves 78 which receive pins 79 depending from the holders 25, 26. The result is that when the rear slide is moved forwardly the pins 79 ride in the transverse slots 78 and pivot the blade holders 25, 26 to swing the blades 28 in unison about a common centre P. Movement of the slides 38, 39 is effected manually by a lever 50 pivoted at 51 and connected to an arm 56 and link 57 through a slip friction clutch 55. The other end of link 57 is pivoted to a lever 58 which is pivoted on the guide block 21 and has a cam face 60 arranged to bear against the end of the slide 38 and move it inwardly when the lever is swung anticlockwise against the tension of a spring 61 stretched between bolts 62, 63 on the slide and guide block respectively. The inner end of lever 50 is formed with a wide notch 70 to receive a pin 69 on the slide 39, thereby providing a lost motion to ensure that slide 39 does not move inwardly until slide 38 has practically completed its full movement, which is determined by an adjustable stop screw 53 thereon in conjunction with a stop pin 54 on the guide plate 21. Following the formation of the first bend in the coiled filament the bight 36 is placed around a hook 35, Fig. 11, on a plate 34 secured above the path of the right-hand finger 28, the unformed portion of the coil being located between the plate 34 and the head 24. After formation of the second bend the first bight is removed from the hook and its place taken by the second, and so on until the required number of coil segments have been formed. The filament is finally mounted in a jig and heat treated to set it in position.